The present invention relates to electrodeposited copper foil; to a method of evaluating physical properties of the electrodeposited copper foil; and to a copper-clad laminate employing the electrodeposited copper foil.
Conventionally, copper foil has been employed as a material for producing printed wiring boards, which are widely used in the electric and electronics industries. In general, electrodeposited copper foil is bonded, through hot-pressing, onto an electrically insulating polymer material substrate such as a glass-epoxy substrate, a phenolic polymer substrate, or polyimide, to thereby form a copper-clad laminate, and the thus-prepared laminate is used for producing printed wiring boards.
In conventionally carried out hot-pressing, a copper foil, a prepreg (substrate) which is cured into a B-stage, and mirror plates serving as spacers are laid-up in a multilayered manner, and the copper foil and the prepreg are hot-press-bonded at high temperature and pressure (hereinafter the step may be referred to as xe2x80x9cbatch-press-laminationxe2x80x9d), to thereby produce a copper-clad laminate.
However, in recent years, reducing the production costs of commercial copper foil products has been an essential issue for maintaining the global competitiveness in the electric and electronics industries. Thus, there is intense demand for reduction in production costs and, further, reduction in the price of printed wiring boards serving as principal components of electronic apparatus.
To meet the demand, a variety of efforts have been made to reducing costs of copper-clad laminates and electrodeposited copper foil, which are intermediate products for producing printed wiring boards. For example, instead of FR-4, CEM-3 has been employed as a copper-clad laminates, and a continuous lamination method has been employed so as to remarkably enhance productivity.
However, the aforementioned alteration in material and method of production results in adverse effects on copper-clad laminates, which effects have never been observed. Thus, an electrodeposited copper foil, serving as a basic material, is required to have characteristics to overcome the adverse effects. In particular, the problems which arise after an electrodeposited copper foil has been bonded to a substrate include bow or warpage, twist, and poor dimensional stability of the copper-clad laminates.
As one solution to the aforementioned problems, Japanese Patent Application Laid-Open (kokai) No. 2-258337 discloses employment of an electrodeposited copper foil exhibiting excellent high-temperature elongation (HTE) characteristics (hereinafter referred to as xe2x80x9cS-HTE foilxe2x80x9d); i.e., an elongation as high as more than 10% in an atmosphere of 180xc2x0 C. Although attempts have been made to solve the aforementioned problems by controlling tensile strength in an atmosphere of 180xc2x0 C., as disclosed in Japanese Patent Application Laid-Open (kokai) No. 5-24152, the problems have not yet been solved completely.